The present invention relates to apparatus for processing signals transmitted on a plurality of different channels, such as a CODEC (Coder/Decoder). The present invention also relates to a communication terminal using an apparatus for multi-channel signal processing.
A conventional signal processing apparatus, which processes a single channel of signals, includes a signal processor connected at an input terminal to an analog/digital (A/D) converter and at an output terminal to a digital/analog (D/A) converter. The other output terminal of the signal processor is connected to a compressor, which compresses a processed signal to generate an output signal. The other input terminal of the signal processor is connected to an expander, which expands a digital input signal to generate a signal to be processed in the signal processor.
The signal processor includes a PROM (Programmable ROM), storing necessary program for signal processing; a decoder, which decodes the program stored in the PROM; a DROM (Data ROM); and a RAM. The signal processor may further include a multiplier; an adder; an accumulator; and a data bus.
In the signal processor, a predetermined processing, such as filtering, is carried out to digital signals on a single channel in accordance with the program read from the PROM.
Recently, it has been required to process different channels of digital signals in a circuit, such as a CODEC. However, when a plurality of different channels of signals is processed in a circuit, electric current flowing therein increases and some problems, such as power supply voltage noise, etc. are created.
Accordingly, an object of the present invention is to provide an apparatus for multi-channel signal processing, in which undesirable electric current is decreased.
Another object of the present invention is to provide a communication terminal unit having a signal processor, which operates with a low noise of power supply voltage.
Additional objects, advantages and novel features of the present invention will be set forth in the description that follows, and will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out herein.
According to a first aspect of the present invention, a signal processing apparatus includes a first signal processor which processes a first channel of signal; and a second signal processor which processes a second channel of signal independently from the processing by the first signal processor.
In the above described first aspect of the present invention, preferably, the first signal processor operates in accordance with a first clock, and the second signal processor operates in accordance with a second clock. And, the first clock and second clock may be shifted in phase so that electric current flowing in the apparatus is dispersed and decreased.
According to a second aspect of the present invention, a communication terminal unit includes the signal processing apparatus of the above-described first aspect of the present invention.